Okay. I did some digging, and this is a great advertising shop. I hope it helps you out♡.

"Only Mango OK" ✯Advertisement Shop✯
http://www.asianfanfics.com/story/view/view/1250938

personally i haven't used any advertising shops but i do see my voice advertisements and mystic multi shop ads around quite often so those should be good. i don't know anything about speed of request fulfillment or anything like that though

links:
my voice advertisements: https://www.asianfanfics.com/story/view/1169480/my-voice-advertisements-closed-til-aug-4th-hiring-advertisers-with-or-without-experience-re-read-chapter-53-i-edited-some-things-taeyeon-hiring-advertisement-advertisementshop-advertising-adshop
mystic multi shop: https://www.asianfanfics.com/story/view/1008399/mystic-multi-shop-advertising-and-graphics-open-for-advertising-and-closed-for-graphics-free-ads-in-chapters-1-and-100-graphics-advertise-hiring-graphicshop-advertisement-advertisementshop-advertising

I do know of a few good ones. Let me hunt them down and I'll get back to you on that.

We Are One multishop by sehun4 has also ads so please check it out, it's one of the two shops where I work so I know it's a good one

http://www.asianfanfics.com/story/view/1257528/we-are-one-multishop-busy-finishing-requests-hiring-not-taking-requests-for-trailers-at-this-time-apink-fxband-graphics-poster-review-snsd-superjunior-trailer-hiring-beta-exo-postershop-betareading-advertisement-reviewshop-betareader-trailershop-advertisementshop-advertising-redvelvet-nct

It's busy at the moment but I am sure you can request soon n,n
I hope this helped